The present invention relates to a glass panel including a pair of glass sheets with a gap being formed between opposing faces of the sheets and the gap being hermetically sealed by peripheral edges of the glass sheets. The invention relates also to a method of manufacturing such glass panel.
For a double glazing or glass panel having peripheral edge thereof sealed, it has been conventionally proposed to bond and seal the entire peripheral edges of the opposing faces of the pair of glass sheets by using metal material such as solder. However, the glass sheets generally do not directly wet with the molten metal material. For this reason, it has been a conventional practice to form, in advance, a metallic coating film having good wettability with the solder at bonding portions on the opposing faces of the pair of glass sheets and then to bond the solder with the glass sheets via such metallic coating film. As such soldering method and the manufacturing method of a bonded assembly of glass sheets utilizing the soldering method, various types of method are known.
For instance, Japanese laid-open patent publication (Kokai) No. Sho. 53-145833 discloses a multiple glazing including two or more glass sheets having metallized edge portions, metallized with e.g. copper coating, thereof soldered.
Further, Japanese laid-open patent publication (Kokai) No. Sho. 54-81324 discloses art of assembling respective components for forming an enclosure in hermetic manner, with at least one of the components being glass. In this, there is disclosed a method of bonding, by means of solder, portions to be bonded which portions have been metallized in advance by e.g. vapor evaporation process.
Still further, Japanese patent publication (Kokoku) No. Hei. 1-58065 discloses, as a high-airtight soldering multiple layer, a multiple layer consisting of a bottom layer, a middle layer and a top layer, which comprises Cu and NiCr films or the like formed on a surface of a base material such as glass.
Further, as the soldering methods, such methods have been attempted as inserting a metal element as an intermediate element between glass substrates having metallic coating films at bonding portions thereof and then bonding these glass substrates and the metallic element by means of solder or as coating solder in advance at the peripheral edges of the glass substrates having metallic coatings and then heating under pressure the substrates so as to bond them together. In either case, the solder employed contains a large amount of lead.
However, with those methods disclosed by the prior art, it has been difficult to obtain hermetically sealed glass panels with good reproducibility. Namely, with such glass panels soldered via the metallic coating films formed at the bonding portions of the glass sheets, sufficient mechanical strength can be obtained, but they are unsatisfactory in the respect of the hermetic seal. This is because of the presence of different material interfaces not only between the respective glass sheets and the solder, but also between the solder and the metal coating film as well as between the metal coating film and each glass sheet. The presence of such interfaces is very disadvantageous for hermetic seal.
Further, in actual manufacturing process, there tend to occur irregularities in the fused condition of the solder at the time of bonding. Because of this, it sometimes happens that the base soldering metallic coating film may be dissolved in the solder completely, thus resulting in insufficient bonding between the solder and the respective glass sheets or that oxidation may develop before the solder can wet the glass sheets, thus leading to deterioration in the hermetic seal.
Also, in the case of the method of bonding glass sheets pre-coated with solder, it is difficult to completely eliminate, at the time of bonding, any oxide dross present originally on the solder coating surface so as to preclude even microscopic inclusions thereon. For this reason, the bonding would be poor in terms of hermetic seal and unsatisfactory especially as vacuum seal.
In addition to the above, if solder with high lead content is employed, the lead may be eluted from the sealed portion of the glass panel when the panel is exposed under such environment as exposure to acid rain, so that there is the possibility of giving adverse effect to the environments.
As described above, the prior art has taught no specific requirements regarding the bonding condition between the glass sheets and the metal required for providing hermetic seal. In particular, it has been practically difficult to manufacture a relatively large glass panel such as one for use in a windowpane in a building. The present invention has been made to solve such problems. Its object is to provide a glass panel including a pair of glass sheets having their peripheral edges sealed in hermetic manner. Another object is provide a glass panel which is free from elution of lead, thus giving no adverse effect to the environments.
The characterizing features of a glass panel and its manufacturing method are as follows.
A glass panel, as shown in FIGS. 2 and 3, includes a pair of glass sheets disposed in a spaced relationship with each other with forming a gap therebetween, peripheral edges of the glass sheets being bonded directly by a single metal material for sealing the gap hermetically, characterized in that the panel satisfies the following relationship:
100xe2x89xa6TLxe2x89xa6(TSxe2x88x92100)
where TL is the liquidus temperature (xc2x0 C.) of the metal material and TS is the strain point (xc2x0 C.) of the glass sheets.
As is the case with the prior art described hereinbefore, when soldering metallic coating films are formed in advance on the peripheral edge of the pair of glass sheet and then metal material is applied between these metallic coating films, microscopic gaps which can serve as passages for gas molecules tend to be formed at such different material interfaces between the glass sheet surface and the metallic coating film and between the metallic coating film and the metal material.
On the other hand, according to the above construction of the invention, the bonding to the glass sheets employs a single metal material without using any soldering metallic film coatings. Therefore, it is possible to maintain air-tightness at the peripheral edges of the glass sheets.
In the above, what is referred to as xe2x80x9cdirect bonding between the glass sheets and the metal materialxe2x80x9d as used in the concept of the present invention means that the only different material interface present is the interface between each glass sheet and the metal material. And, the term: xe2x80x9csingle metal materialxe2x80x9d refers to a single element metal or an alloy having a certain composition to be used alone between the pair of glass sheets. For instance, sealing by using two or more kinds of solder having different compositions from each other is obviously excluded from the scope of the invention. Also, a condition of any other substance than the metal material being present at the bonding portion is contrary to the concept of the invention. Namely, when solder-coated glass sheets are bonded by heating with each other, the inclusions originated from the oxides formed on the raw solder material is contained within the solder, tending to result in reduction in the air-tightness. Further, the residual substance such as flux commonly employed for preventing oxidation of solder must not be present at the bonding portions since it deteriorates the air-tightness. That is to say, the conventional method involving the preliminary formation of the metal coating film for solder welding and a glass panel obtained by such method are out of the scope of the present invention.
With the bonding technique of coating the glass sheet surfaces with solder in advance and then boding the sheets face to face, the oxides on each solder surface will remain to form a different material interface. Therefore, such technique too is out of the scope of the present invention. Namely, the method taught by the prior art is contrary to the concept of the present invention.
As described hereinbefore, the present invention is characterized in that the air-tightness is provided by direct bonding between the glass sheet and the single metal material. However, the scope of the present invention does not exclude presence of other metal material, inorganic material or organic material at or in the vicinity of the bonding portions. That is to say, it is possible to dispose in advance a wire element, powder or the like formed of other metal material than the sealing metal material at the bonding portions of the glass sheets and then to charge the sealing metal material at these bonding portions so that a certain component contained in the wire element, powder material or the like may dissolve into the sealing metal material for improving the bonding strength or to coat bonding portions with an inorganic material, organic material or the like for protection from the environment. These modified constructions are not contrary to the concept of the invention.
Then, the glass panel according to the invention is characterized in that the panel satisfies the following relationship:
100xe2x89xa6TLxe2x89xa6(TSxe2x88x92100)
where TL is the liquidus temperature (xc2x0 C.) of the metal material and TS is the strain point (xc2x0 C.) of the glass sheets.
Here, the term: xe2x80x9cliquidus temperature TL of the metal materialxe2x80x9d refers to the temperature at which the metal completely becomes a liquid phase when heated from a lower temperature. Such temperature can be determined by the differential thermal analysis for instance.
Further, the term: xe2x80x9cstrain point TS of the glass sheetxe2x80x9d refers to the temperature at which the glass has a viscosity of 4xc3x971014 (dPa.s) (4xc3x971014 poise).
In general, the metal material is to be bonded with a glass sheet while the metal material is in its molten condition. Therefore, in order to avoid deformation of the glass sheet, it is desired that the liquidus temperature TL (xc2x0 C.) be lower than the strain temperature TS (xc2x0 C.) of the glass sheet to be bonded. With this, it becomes possible to effect the bonding within a temperature range where the deformation of the glass sheet is small. Further, in order to minimize the stress resultant from a difference in thermal expansion between the glass sheet and the metal material which stress can lead to breakage, it is desired that the bonding be effected at a lowest possible temperature. As a rule of thumb, it is preferred that TL be lower than TS by 100xc2x0 C. or more. In its daily use, the glass panel can be heated to a considerably high temperature when exposed to a strong sunbeams during summer. In such case, if TL is too low, the strength will be reduced. For this reason, it is preferred that TL be higher than 100xc2x0 C. It is more preferred that TL be higher than 150xc2x0 C.
To summarize the above, the preferred relationship between the liquidus temperature TL (xc2x0 C.) of the sealing metal material and the strain point TS (xc2x0 C.) of the glass sheets to be bonded is: 100xe2x89xa6TLxe2x89xa6(TSxe2x88x92100). Then, the liquidus temperature of the metal material is adjusted so as to satisfy the above relationship by appropriate adjustment of the ratio of its components.
The glass panel according to a preferred embodiment is characterized in that the lead content in the metal material is below 0.1 wt. %.
With this construction, even when the glass panel is exposed to a severe environment such as exposure to acid rain, there occurs no elution of lead, thus providing no adverse effect to the environment.
The glass panel according to a preferred embodiment is characterized in that the metal material contains two or more kinds of components selected from a group consisting of Sn, Zn, Al, Si and Ti.
With this construction, the contained components and oxygen present on the glass sheet surfaces will be bonded to each other to improve the bonding strength.
As the metal material to be used at the bonding portions according to the present invention, solder having the above-defined components and range of composition may be cited. More preferred range of composition and the reasons thereof are as follows. In the following discussion, the compositions and component ratios are represented as weight %.
Sn is non-toxic and provides the function of providing wettability to the object to be bonded.
Zn provides a bonding force to oxide materials such as glass, ceramics, etc. If the addition amount of Zn is too large, there occurs increasing tendency of brittleness of the solder, hence not desirable for actual use. The preferred range of its addition amount is 0.5xcx9c10%.
The binary system of Sn and Zn is an eutectic system. With eutectic composition, the composition can easily become an alloy having fine structure by cooling from its molten condition. The eutectic point corresponds to the composition of Sn 91% and Zn 9%. At its eutectic temperature 198xc2x0 C., a liquid phase and two solid phases of Sn and Zn coexist. This eutectic composition can easily become a fine metal structure by cooling and solidifying, as described above. So that, this composition is flexible, thus being advantageous for relaxing stress generated in the course of the bonding operation with the glass sheets, thus improving the bonding strength. Accordingly, it is preferred that the solder contain Sn and Zn in a ratio approximating such eutectic composition thereof. In particular, it is preferred that Zn be present at 8 to 10% relative to the sum of Sn and Zn.
Al is an element which can be oxidized very easily, but it provides the advantageous effect of being readily bonded with an oxide. Such effect will be low if the addition amount of Al is below 0.001%. Whereas, if it exceeds 3.0%, this will result in increase in the hardness of the solder per se. Hence, it becomes difficult to ensure heat-cycle resistance and the melting point will rise to deteriorate the workability. Then, the preferred range of its addition amount is 0.001 to 1.0%.
Si is also an element which can be oxidized very easily, but it provides the advantageous effect of being readily bonded with an oxide. With a small addition amount, it will be effective for rendering the metal structure finer during the cooling/solidifying process, so as to increase the flexibility of the solder. This effect will be low if the addition amount of Si is below 0.001%. Whereas, if it exceeds 3.0%, this will result in increase in the hardness of the solder per se. Hence, it becomes difficult to ensure heat-cycle resistance and the melting point will rise to deteriorate the workability. Then, the preferred range of its addition amount is 0.001 to 1.0%.
Ti is also an element which can be oxidized very easily, but it provides the advantageous effect of being readily bonded with an oxide. Further, since Ti has a large oxygen solubility, it is effective for causing the solder to contain oxygen. That is, with Ti, it becomes possible for the solder to contain oxygen in the form of Tixe2x80x94O, without elution of oxides. And, this oxygen promotes the formation of bonding to the glass, as will be detailed later. This effect will be low if the addition amount of Ti is below 0.001%. Whereas, if it exceeds 3.0%, this will result in increase in the hardness of the solder per se. Hence, it becomes difficult to ensure heat-cycle resistance and the melting point will rise to deteriorate the workability. Then, the preferred range of its addition amount is 0.001 to 1.0%.
The glass panel according to a preferred embodiment is characterized in that the metal material contains O (oxygen) in the range from 0.0001 to 1.5 wt. %.
For instance, by the presence of oxygen in the dissolved form within the metal material, it is possible to promote the formation of the bonding at the interface between the glass sheet and the metal material. In order to cause the metal material to contain oxygen, this is possible by either or both of melting and producing the metal material in an oxygen-containing atmosphere and carrying out the bonding with the glass sheets in an oxygen-containing atmosphere.
Oxygen is a component which promotes bonding between the metal material and the glass. With oxygen being present in an dissolved form within the metal material, at the interface between the glass and the metal material, the transition from the oxide bonding to the metal bonding can occur smoothly, thereby to reinforce the bonding interface. This effect will be low if the oxygen concentration is too low. On the other hand, if the concentration is too high, this will tend to invite elution of oxide in the metal material. Then, the oxygen concentration should preferably be 0.0001% or higher, more preferably 0.001% or higher, and yet preferably should range between 0.001 and 1.5%. The preparation of such oxygen-containing metal material is possible by melting the metal material in an oxygen-containing atmosphere, e.g. an ambient atmosphere. And, its oxygen content can be increased or decreased by appropriately adjusting the melting temperature, period, etc. Further, even if the metal material does not contain oxygen before it is used for the bonding operation, the metal material after the bonding operation may contain a preferred concentration of oxygen by appropriately adjusting the atmosphere in which the bonding is carried out. In such case, substantially same high bonding strength may be obtained as use of the oxygen-containing metal material.
The glass panel according to a preferred embodiment as illustrated in FIGS. 4-8, is characterized in that the pair of glass sheets have different dimensions so that one glass sheet is disposed in opposition to the other glass sheet with the one sheet projecting at a peripheral edge thereof by a width of 1 to 10 mm from each peripheral edge of the other sheet, with the metal material being charged from the projecting portion of the one glass sheet into the gap between the glass sheets.
With this construction, not only the gap but also the end faces of the glass sheets can contribute to the bonding, whereby the bonding strength may be improved.
The glass panel according to a preferred embodiment is characterized in that the gap is sealed to keep a depressurized condition.
With this construction, it is possible to reduce the thermal conductance, whereby a glass panel having superior heat insulating performance may be obtained.
A method of manufacturing a glass panel according to a preferred embodiment as illustrated in FIG. 1, is characterized by the steps of: disposing spacers between the pair of glass sheets to form a gap therebetween; charging a molten single metal material to the peripheral edges of the glass sheets, the metal material satisfying the following relationship:
100xe2x89xa6TLxe2x89xa6(TSxe2x88x92100)
where TL is the liquidus temperature (xc2x0 C.) of the metal material and TS is the strain point (xc2x0 C.) of the glass sheets; and directly bonding the glass sheets and the metal material together so as to seal the gap hermetically.
With the conventional method, e.g. a metal coating film for bonding with molten solder is provided on the surface of each glass sheet for sealing bond. In such case, a number of different material interfaces exist between the glass sheet surface and the metal coating film, between the metal coating film and the solder, etc.
On the other hand, in the case of the invention""s method in which a single metal material is charged to the peripheral edges of the glass sheets, only two different material interfaces are present, so that its number can be minimized. Accordingly, microscopic gaps will hardly be formed at the different material interfaces, whereby the reliability of the air-tightness at the peripheral edges of the glass sheets may be improved.
In the above, in xe2x80x9ccharging the molten metal material to the peripheral edges of the glass sheetsxe2x80x9d, it is important that the glass sheets and the metal material be bonded directly with each other. Any oxide generated when the molten metal material comes into contact with an oxygen-containing atmosphere is present on the bonding interface, this will result in reduction in bonding strength, making it difficult for the assembly to withstand its evacuated air-tightness as well. For this reason, such oxides must be eliminated as much as possible.
And, in this method, the method employs the metal material which satisfies the following relationship:
100xe2x89xa6TLxe2x89xa6(TSxe2x88x92100)
where TL is the liquidus temperature (xc2x0 C.) of the metal material and TS is the strain point (xc2x0 C.) of the glass sheets. Then, in bonding the molten metal material with the glass sheets, it is possible to prevent deformation in the glass sheets. Further, by minimizing the stress occurring from a difference in thermal expansion between the glass sheets and the metal material, it is possible to prevent breakage of the glass sheets also.
The method of manufacturing a glass panel according to a preferred embodiment is characterized by the steps of: heating and maintaining the pair of glass sheets at a temperature below the liquidus temperature of the metal material, the molten metal material having a portion coming into contact with an atmosphere and a further portion not coming into contact with the atmosphere before the metal material is charged into the gap between the glass sheets; and charging into the gap at the peripheral edge of the glass sheets only the portion of the metal material which did not come into contact with the atmosphere, while preventing the portion which came into contact with the atmosphere from being charged into the gap.
With the above method, by heating the glass sheets to a temperature below the liquidus temperature of the metal material, the wettability of the glass sheets may be improved for facilitating the charging operation of the metal material.
Further, the reason for the prevention of the portion which came into contact with the atmosphere from being charged into the gap is as follows.
Namely, if the metal material contains a component having a large affinity relative to oxygen, even a small amount of oxygen in the atmosphere can cause development of oxidation in the metal material. For this reason, it will become necessary in general to carry out the bonding operation with the glass sheets in an inert atmosphere or under a depressurized condition. In this, according to the invention""s method, only the inner portion of the metal material coated with oxides is caused to permeate into the gap, thereby to prevent the oxides formed on the surface thereof from entering the bonding portion.
The method of manufacturing a glass panel according to a preferred embodiment as shown in e.g. FIGS. 11 and 12, is characterized that the step of charging the molten metal material into the gap between the glass sheets employs a guide for guiding the metal material to the gap, at least a portion of the guide being inserted into the gap.
In the above, the xe2x80x9cguidexe2x80x9d refers to a member adapted for guiding the molten metal material from an outlet of its feeding device to the gap between the glass sheets. The molten metal material is guided to the target position by its wetting with the guide as well as by the restriction of its flow by the shape of the guide.
With the method described above, as the guide is provided, the introduction of the metal material into the gap, which tends to be difficult in the case of a narrow gap, can be promoted and facilitated, and the introducing speed may be increased, so that the above-described direct bonding between the metal material and the glass sheets may be formed easily.
The method of manufacturing a glass panel according to a preferred embodiment, as shown in e.g. FIGS. 11 and 12, is characterized in that the guide is a plate-like or bar-like guide.
With the guide having such shape as above, by appropriately setting e.g. the thickness of its plate-like portion or the diameter of its bar-like portion, this guide may be inserted into the gap, regardless of the size of this gap between the pair of glass sheets. Accordingly, the charging operation of the metal material may be carried out in a reliable manner.
The manufacturing method of a glass panel according to a preferred embodiment, as shown in e.g. FIGS. 13 through 16, is characterized in that the method employs a stimulus conducting member for physically stimulating the interface between the molten metal material and the glass sheet surface so as to promote the direct bonding therebetween, at least a portion of the stimulus conducting member being inserted into the gap.
In the above, the xe2x80x9cstimulus conducting memberxe2x80x9d refers to a member capable of conducting a physical stimulus to the molten metal material of the gap. By applying a physical stimulus to the molten metal material, any oxides etc. which can interfere with the direct bonding at the interface between the metal material and the glass can be eliminated forcefully, so that a more firm and dense bonding interface suitable for the hermetic sealing may be obtained.
The manufacturing method of a glass panel according to a preferred embodiment, as shown in e.g. FIGS. 13 through 16, is characterized in that the stimulus conducting member is a plate-like or bar-like member.
As described above in connection with a preferred embodiment, with the stimulus conducting member having such shape as above, by appropriately setting e.g. the thickness of its plate-like portion or the diameter of its bar-like portion, a portion of this member may be inserted into the gap, so that the physical stimulus for promoting the direct bonding at the interface between the metal material charged at the gap and the glass may be applied in an efficient and effective manner.
The manufacturing method of a glass panel according to a preferred embodiment, as shown in e.g. FIGS. 13 through 16, is characterized in that the physical stimulus for promoting the direct bonding is provided by mechanical movement of the stimulus conducting member.
In general, the molten metal material to be charged into the gap has a certain viscosity. Then, with the method of the invention in which the stimulus conducting member inserted into the gap is mechanically moved, the metal material charged into the gap is forcibly moved, so that the physical stimulus for promoting the direct bonding at the interface with the glass can be applied in an efficient and effective manner.
The method of manufacturing a glass panel according to a preferred embodiment, is characterized in that unevenness is provided on a surface of the stimulus conducting member.
In the above xe2x80x9cunevennessxe2x80x9d includes grooves and projections. With this unevenness, the interface between the molten metal material and the glass may be effectively renewed. For instance, as the friction between this stimulus conducting member and the molten metal material is improved thus further increasing the physical stimulus, the molten metal material may be stirred strongly. As a result, it is possible to forcibly eliminate oxides of the metal material which would otherwise tend to remain at the interfaces.
Further, if the stimulus conducting member and the glass come into contact with each other so that the molten metal material is charged while rubbing also the surface of the glass sheet, the physical stimulus is further increased and the components of the metal material and the components of the glass can come into more direct contact with each other. So that the bonding will become stronger and denser, thus contributing to formation of superior bonding interface therebetween.
The manufacturing method of a glass panel according to a preferred embodiment, as shown in FIGS. 11-16, is characterized in that the guide and/or stimulus conducting member is moved along the gap.
With the above method, the peripheral edge of a glass panel having a long side may be sealed easily.
Also, in the case of such movement of the stimulus conducting member, this mechanical movement of the stimulus conducting member can also serve as physical stimulus for promoting the direct bonding.
The manufacturing method of a glass panel according to a preferred embodiment is characterized in that the mechanical movement of the stimulus conducting member is at least either of rotation and vibration. If the mechanical movement to be applied is either rotation or vibration, this makes it easier to make the device. The, with using such simple device, the peripheral edge of the glass panel may be sealed reliably.
The manufacturing method of a glass panel according to a preferred embodiment is characterized in that at least one of the guide and the stimulus conducting member is made of a metal material.
If the guide or the stimulus conducting member is formed of a metal material as above, a guide or stimulus conducting member having desired strength, corrosion resistance, etc., may be obtained easily.
Incidentally, the guide or the stimulus conducting member may be formed alternatively of ceramics etc, depending on the necessity.
The manufacturing method of a glass panel according to a preferred embodiment, is characterized in that the guide and the stimulus conducting member are provided as a single member having the functions of both of them.
With this method, the molten metal material may be easily inserted into the gap and also the bonding interface between the glass sheets and the molten metal material may be formed efficiently.
The manufacturing method of a glass panel according to a preferred embodiment, as shown in FIGS. 4-8, is characterized in that the pair of glass sheets have different dimensions from each other and one glass sheet is disposed in opposition to the other glass sheet with a peripheral edge of the former projecting from a peripheral edge of the latter by a width of 1 mm through 10 mm, and the metal material is charged from the projecting portion of the one glass sheet toward the gap by utilizing capillary phenomenon.
With this method, by disposing one glass sheet on the lower side, the molten metal material can be introduced into the gap via the projecting portion. Hence, the charging operation of the molten metal material may be facilitated.
The manufacturing method of a glass panel according to a preferred embodiment, as shown in FIGS. 17 and 18, is characterized in that the pair of glass sheets are heated and maintained at a temperature below the liquidus temperature of the metal material and under this condition, vibration is applied to at least one of the molten metal material or the glass sheet, so as to cause the material to permeate and to be charged into the gap by utilizing capillary phenomenon.
That is, with the above method, the molten metal material with its wettability to the glass sheets improved by the application of vibration thereto is caused to permeate, by its own force commonly referred to as capillary phenomenon, into the peripheral edge to fill the gap. With this method, the formation of the dissimilar material interface which would occur with the prior art described hereinbefore can be minimized, so as to achieve a favorable condition for air-tightness. As a method of applying vibration, in addition to the method of placing the vibrating member in direct contact with the molten metal material for applying or applying the vibration to the glass sheets, it is also possible to vibrate the metal material without physical contact by means of e.g. electromagnetic induction.
Incidentally, by heating the glass sheets, the wettability between the molten metal material and the glass sheets may be improved; hence, the permeation/charging of the metal material into the gap is promoted to improve the reliability of the hermetic sealing.
The manufacturing method of a glass panel according to a preferred embodiment, is characterized in that the vibration includes two or more kinds of frequencies and either one or both of them is/are applied to at least one of the metal material and the glass sheet.
The degree of the capillary phenomenon of the molten metal material relative to the gap is believed to vary, depending on such factors as the temperature of the molten metal material, the size of the gap, etc. With the capillary phenomenon in general, the smaller the gap, the greater the force which urges the liquid to enter it. On the other hand, this will reduce the cross section area of the area (inlet) through which the liquid enters the gap, thus increasing the resistance at this area. Then, by providing two or more kinds of frequencies, it is possible to obtain a good balance between the permeating force and the resistance at the inlet, thus allowing the capillary phenomenon to take place in a most efficient manner, thereby stabilizing the permeation of the molten metal material into the gap.
The manufacturing method of a glass panel according to a preferred embodiment, is characterized in that the two or more kinds of vibrations having different frequencies of either a low frequency of 1 Hz to 10 kHz or a supersonic frequency of 15 to 100 kHz.
With the above method, by applying the low frequency vibration of 1 Hz to 10 kHz, the resistance at the inlet encountered by the molten metal material to permeate into the gap may be reduced, so that the material may permeate into the gap in an efficient manner.
Further, by applying the supersonic frequency of 15 kHz to 100 kHz, it is possible to restrict formation of the oxide coating film of the metal material at the bonding interface.
Incidentally, when the frequency of the vibration to be applied is 15 kHz to 100 kHz, the favorable effect can be achieved as described above. With a range over 15 kHz, the formation of oxide coating film of the metal material at the bonding interface may be restricted, so that a satisfactory performance for practical use may be obtained and the device may be inexpensive and easy to handle. To be more specific, the most preferred range is 15 kHz to 80 kHz.
Further, if vibration ranging between 800 kHz and 10 MHz, this will be effective for improving the adherence between the metal material and the glass sheet, whereby even denser and stronger bonding interface may be obtained.
The manufacturing method of a glass panel according to a preferred embodiment is characterized in that the metal material has a lead content below 0.1 wt. %.
With this method, even when the glass panel is exposed to a severe environment such as acid rain, no elution of lead will occur. So that, it is possible to obtain a glass panel which does not give any adverse effect to the environment.
The manufacturing method of a glass panel according to a preferred embodiment is characterized in that the metal material contains two or more kinds of components selected from a group consisting of Sn, Zn, Al, Si and Ti.
With this method, the contained components and oxygen present on the glass sheet surfaces will be bonded to each other to improve the bonding strength.
The manufacturing method of a glass panel according to a preferred embodiment is characterized in that the metal material contains O (oxygen) in the range from 0.0001 to 1.5 wt. %.
With this method, by the presence of oxygen in the dissolved form within the metal material, it is possible to promote the formation of the bonding at the interface between the glass sheet and the metal material.
The manufacturing method of a glass panel according to a preferred embodiment is characterized in that the gap is sealed to keep a depressurized condition.
With this method, it is possible to reduce the thermal conduction, whereby a glass panel having superior heat insulating performance may be obtained.